DESCRIPTION (provided by candidate): On the cellular and molecular level, exactly how humans sense touch is poorly understood. Even a slight breeze exerts enough pressure against the skin to start a rapid signaling cascade that immediately transmits the sensation to the brain. This process of translating mechanical stimuli into neuronal signals is called mechanosensation, and it is critical for the sense of touch, hearing, balance, kidney regulation, and more. Integral components of mechanosensation are proteins embedded within the surface of a cell called ion channels that open upon tension or stretch. In mammals epithelial sodium channels (ENaCs) and acid- sensing ion channels (ASICs) are linked to mechanosensation, but little is known about how they function in this process. C. elegans is a model organism often used for studying mechanosensation. The two C. elegans proteins that are the focus of this proposal, MEC-4 and MEC-10, constitute the channel that senses gentle touch and are in the same super family as ENaCs and ASICs. Thus, information gained from studying MEC-4 and MEC-10 in their native environment will be relevant to mammalian touch sensation. Many of the residues that line the pore of the channels in this super family are highly conserved, and they have long been implicated in channel function. In this proposal highly conserved residues found in the pore of the channel formed by MEC-4 and MEC-10 will be mutated in order to determine how specific changes alter channel function in vivo using the slit-worm whole-cell patch clamp technique. Determining the roles of these residues will enhance the understanding of channel gating at the molecular protein level. First, mutations with known phenotypes will be studied. Then, the many pore-lining glycines will be investigated to probe the importance of the GxxxG helix-packing motif in the gating pathway of the channel. This work will be the first thorough in vivo electrophysiological investigation of this important region. Mechanosensitive protein channels are involved in many vital processes such as interpreting the sensations of touch and hearing, regulating kidney function, controling blood pressure, and balancing the ratio of salt and water across cells. Understanding how these channels function could open the door to interventions that prevent or slow the decline of the important human functions that they control.